An image forming apparatus such as a printer and a copier generally includes a plurality of rollers. For example, an electrophotographic image forming apparatus generally includes a photosensitive drum, a development roller, a transfer roller, a plurality of conveyance rollers, and so on. An inkjet image forming apparatus includes a plurality of conveyance rollers and so on.
Such image forming apparatuses have drive transmission devices for transmitting driving force from drive sources (for example, motors) to the rollers. A drive transmission device has a coupling for connecting a driving shaft and a driven shaft (for example, Patent Literature 1). In the coupling device described in Patent Literature 1, the driving shaft has engagement faces inclined toward the center of rotation thereof by which the center of rotation of the driving shaft and the center of rotation of the driven shaft are aligned.